The present invention relates to a device for planetary electrode-wire-feeding in automatic and semi-automatic electric-arc welding machines, wherein the pushing force that is applied to the electrode-wire is automatically adjusted.
A device has been developed for the same purpose wherein the pushing force applied to the electrode-wire is also automatically adjusted. In this other device, developed by the applicants, a housing is provided in which there are machined a pair of bores extending radially relative to the feed direction of the electrode wire. A pair of pistons are movably seated in the bores, each piston supporting rotatably a feed roller and the axes of these feed rollers are skewed relative to each other. The electrode-wire is fed between the feed rollers.
The other side of the housing is formed as a hollow cylindrical threaded part onto which a guide cone having a threaded internal bore is threadably mounted. The guide cone is drivably connected to an electric motor. A pair of double-armed levers are mounted on the housing by means of articulated joints. One of the ends of the double-armed levers are in contact with the guide cone surface and the other ends are in contact with the respective piston heads. The double-armed levers lie in a plane which passes also through the electrode-wire. The axes of the pistons also pass through this same plane. The pistons can be formed with blind holes in which springs are mounted. The springs press the pistons continuously toward the double-armed levers as well as toward the electrode-wire via the feed rollers mounted thereon.
The aforedescribed device, which is related to the device of the instant invention and which has been developed by the same joint inventors, has the draw-back of having substantial frictional forces formed when the guide cone and the hollow cylindrical portion of the housing threadably move relative to each other. Such frictional forces retard the movement of one part relative to the other. This retardation causes a concomitant retardation of the engagement and disengagement of the feed rollers with the electrode-wire.
The double-armed levers lie in a plane which is parallel to the direction of pivoting of the levers and if the direction of pivoting is not rigorously maintained the levers frequently are twisted and then the device malfunctions. Furthermore, the whole arrangement is rather compact and therefore the double-armed levers have relatively short arms and their effectiveness is therefore limited.